| A photoresponsive surfactant, azoTAB, is used to control protein structure. When azoTAB is combined with a protein, illumination with visible and UV light can be used to induce different protein conformational changes. A means to reversibly control the secondary and tertiary structure of two proteins, lysozyme and RNase A, has been developed. In the presence of azoTAB and under visible light illumination, the alpha-domain of lysozyme unfolds, forming a new folding intermediate. Lysozyme transitions from this intermediate back to its native state under UV light illumination. Similarly, in the presence of azoTAB and under visible light illumination, a swollen form of RNase A is observed, which also transitions back to its native state under UV light illumination. Additionally, a means to control the quaternary structure of alpha-chymotrypsin has been developed. The degree of self-association of alpha-chymotrypsin, which readily associates in aqueous solution, is controlled when combined with azoTAB and UV or visible light illumination. Under visible light, the associated form is a corkscrew hexamer. Under UV light, these corkscrews self-associate in a slightly offset manner, forming ropelike dodecamers. The dodecamers were found to be preamyloidal. A means to control the association of a well-known amyloid protein linked to Alzheimer's disease, amyloid-beta peptide, has been developed. When combined with azoTAB and illuminated with visible light, the association of amyloid-beta into fibrils is significantly delayed relative to the association of pure amyloid-beta. UV light can be used to trigger the fibril formation process. In all cases, Small Angle Neutron Scattering was the main tool used to investigate the various changes in protein structure. |
